usb: gadget: tcm_usb_gadge: fix to return error or 0 in tcm_usbg_drop_nexus()

In the error handling case of tcm_usbg_drop_nexus(), the error code
is assigned to 'ret', but it is ignored. We'd better return 'ret'
instead of always return 0.

dpatch engine is used to auto generate this patch.
(https://github.com/weiyj/dpatch)
Signed-off-by: NWei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: NFelipe Balbi <balbi@ti.com>

drivers/usb/gadget/tcm_usb_gadget.c

@@ -1794,9 +1794,10 @@ static int tcm_usbg_drop_nexus(struct usbg_tpg *tpg)
 	tpg->tpg_nexus = NULL;
 
 	kfree(tv_nexus);
+	ret = 0;
 out:
 	mutex_unlock(&tpg->tpg_mutex);
-	return 0;
+	return ret;
 }
 
 static ssize_t tcm_usbg_tpg_store_nexus(